如何在VB.Net中擴展一個類的構造函數？

Question

假設我有：

Public Class clsTest 
    Public Sub New() 
    End Sub 

    Public Sub New(name_ As String) 
     '... 
    End Sub 
End Class 

我想擴大這個類，例如：

<System.Runtime.CompilerServices.Extension> _ 
Public Sub methodA(t1 As clsTest, i As Integer) 
    '... 
End Sub 

但我不能爲擴展構造：

<System.Runtime.CompilerServices.Extension> _ 
Public Sub New(t1 As clsTest, name_ As String, i As Integer) 
    '... 
End Sub 

Answer 1

您cannot extend constructors與擴展方法。擴展方法是幾乎相同的static（shared在VB）方法，它允許寫的

instanceOfMyClass.SomeExtension(someParameter) 

代替

MyClass.SomeExtension(instanceOfMyClass, someParameter) 

如果你沒有存取權限clsTest（你真的應該改變您namings），但你仍要擴展它，你也可以創建一個新的類，從它繼承：

Public Class Foo ' consider this as your clsTest 
    Public Sub New() 
    End Sub 
    Public Property Name As String 
    Public Property Number As Int32 
    Public Sub New(name As String) 
     Me.Name = Name 
    End Sub 
End Class 

Public Class Bar 
    Inherits Foo 

    Public Sub New(name As String, i As Integer) 
     MyBase.Name = name 
     MyBase.Number = i 
    End Sub 
End Class 

翅同盟，也許你不需要延長班級，但你只是尋找一種方便的方式來初始化它在一個單行：

Dim foo = New Foo("test") With {.Number = 4711}